(Reuters) - A federal appeals court on Friday said U.S. Supreme Court precedent precludes claims by a group of Oregon lawyers that mandatory membership in the state bar association violates their free-speech rights, but revived their separate free-association arguments.

A three-judge panel of the 9th U.S. Circuit Court of Appeals said the Supreme Court's 2018 decision in Janus v. AFSCME, which said public-sector unions cannot collect fees from nonmembers, did not overturn the high court's 1990 ruling in Keller v. State Bar of California that allowed state bar associations to require members to pay dues.

The court said that unlike unions, which routinely engage in activities unrelated to collective bargaining, the Oregon State Bar (OSB) requires that dues be used only for activities germane to the regulation of the legal profession, and so the collection of those dues does not violate lawyers' free-speech rights.

But the 9th Circuit said the plaintiffs could pursue a separate argument that mandatory membership in the state bar, independent of compelled financial support, violates their rights to free association, because the Supreme Court has never addressed that question.

Jacob Huebert of the conservative Goldwater Institute and Oregon solo practitioner Michael Spencer, who represent the plaintiffs in two consolidated lawsuits, did not immediately respond to requests for comment. Nor did the OSB, which is represented by Miller Nash Graham & Dunn.

The Goldwater Institute represents lawyers in several similar cases around the country, including a challenge to compulsory bar membership in Louisiana that will be heard by the 5th Circuit next week.

The Supreme Court last June declined to review a 7th Circuit ruling that said Wisconsin's state bar could require lawyers to join and pay dues.

The plaintiffs in the Oregon cases filed two separate lawsuits in 2018, after Janus was decided. Like many state bar associations, the OSB administers bar exams, reviews applicants' character and fitness, and enforces rules of professional conduct.

The lawsuits came after the group in an April 2018 newsletter published statements disavowing white nationalism and related violence and asserting that then-President Donald Trump "has himself catered to this white nationalist movement." The OSB refunded the plaintiffs and other lawyers who complained about the statements $1.15 each, which was the portion of their dues used to published the newsletter.

In the lawsuits, the lawyers said the requirements that they join the OSB and pay dues violated their First Amendment rights, and that the group lacked safeguards to protect the rights of members who object to its activities.

U.S. District Judge Michael Simon in Portland dismissed both cases in 2019. He said that both the free-speech and free-association claims were precluded by the Keller decision, and that the OSB's procedure for issuing refunds was adequate.

The plaintiffs appealed, arguing that the Supreme Court had effectively overturned Keller in the Janus case, and that the OSB's after-the-fact refunds were insufficient to protect members' rights.

The 9th Circuit disagreed on Friday. Although Keller relied on previous Supreme Court precedent that was expressly overruled in Janus, courts cannot take it upon themselves to declare that Keller was no longer sound, the panel said.

But the panel said the Supreme Court has never resolved the broader issue of whether compelled bar membership violates lawyers' rights to free association regardless of whether they must pay dues, and remanded the case to Simon to weigh that issue.

The panel included Circuit Judges Jay Bybee and Lawrence VanDyke and U.S. District Judge Kathleen Cardone of the Western District of Texas, who sat by designation.

The case is Crowe v. Oregon State Bar, 9th U.S. Circuit Court of Appeals, No. 19-35463.

For the plaintiffs: Jacob Huebert of the Goldwater Institute and Michael Spencer

For the state bar: Elisa Dozono of Miller Nash Graham & Dunn